Ground-up rewrite of the data model. Putting this in the ve2 directory for now so we still have the old code floating around.
Main changes so far in this rewrite:
* Renamed hasChildren() to canHaveChildren()
* Added canHaveGrandchildren()
* Added a new node type TwigNode that can have children but not grandchildren (so all of its children must be LeafNodes)
* Implemented push/pop/shift/unshift as wrappers around splice()
* Renamed getElementType() to getType(). Nodes now take a string as a type, and the element stuff is gone and won't be back
* Removed clearRoot(), replaced it with setRoot( this ) where needed
Change-Id: I23f3bb1b4a2473575e5446e87fdf17af107bacf6
This has some TODOs still but I want to land it now anyway, and fix the
TODOs later.
* Add this.offsetMap which maps each linear model offset to a model tree node
* Refactor createNodesFromData()
** Rename it to buildSubtreeFromData()
** Have it build an offset map as well as a node subtree
** Have it set the root on the fake root node so that when the subtree
is attached to the main tree later, we don't get a rippling root
update all the way down
** Normalize the way the loop processes content, that way adding offsets
for content is easier
* Add rebuildNodes() which uses buildSubtreeFromData() to rebuild stuff
* Use rebuildNodes() in DocumentSynchronizer
* Use pushRebuild() in TransactionProcessor
* Optimize setRoot() for the case where the root is already set correctly
Change-Id: I8b827d0823c969e671615ddd06e5f1bd70e9d54c
